1. Field of the Invention
The present invention relates to a novel microbiological method for preparing 2,5-diketo-D-gluconic acid (hereinafter referred to as 2,5 DKG) from D-glucose. Particularly, it is concerned with a method for preparing 2,5-DKG by fermentation of new microorganisms which belong to Erwinia n. sps. or by simple contact of D-glucose with said microorganisms or their processed products, for instance, resting cells, immobilized cells, ground cells or any enzymes extracted therefrom, which may be suspended in a fluid medium or fixed on a surface of a stationary bed.
2. Description of the Prior Art
2,5 DKG is a useful intermediate in the production of L-ascorbic acid. Namely, 2,5 DKG can selectively and stereospecifically be reduced into 2-keto-L-gulonic acid, a precursor of L-ascorbic acid, in a promising new route for the latter product (See, for instance, U.S. Pat. Nos. 3,922,194, 3,959,076, 3,963,574 and 3,998,697).
In all of the known means, the production of 2,5 DKG has been achieved by cultivating aerobic microorganism strains which belong exclusively to genera Acetobacter, Acetomonas, Gluconobacter and Pseudomonas. No instance has hitherto been reported as to its production by means of cultivation using faculatatively anaerobic strains which belong to genus Erwinia.